Protective container for metal sheets or like metallic goods during the process of heat treatment



' w W, W36. ,J. FALLON PROTECTIVE CONTAINER FOR METAL SHEETS OR LIKE METALLIC GOODS DURING THE PROCESS OF HEAT TREATMENT Filed Aug. 6, 1934 Patented Mar. 10, 1936 PATENT OFFHE PROTECTIVE CONTAINER FOR METAL SHEETS on LIKE METALLIC GOODS DURING THE P TREATNIEN T access OF HEAT John Fallon, Birmingham, England Application August 6, 1934, Serial No. 738,614 .In'Great Britain August 29, 1933 2 Claims.

invention has reference to an improved form of container into which metal sheets or other metal goods capable of nesting in a reasonably flat layer can be inserted during the process of heat treatment, including heating and cooling,

of a dish and a cover, the joints between these parts being filled with a luting material such as sand or clay. In the process of heat treatment, during the period in which the goods are being raised in temperature to the necessary degree for correct treatment, the atmosphere within such box-like container expands with heat and escapes through the luting material, which is usually of a porous character. Conversely, on cooling the goods the atmosphere in the container contracts and draws in through the luting material such gases as may surround the container forthe time being, whether furnace gases or special cooling chamber gases or outer atmospheric gases.

The results obtained by these methods, particularly for laminated materials, are not very satisfactory in practice, due primarily to the fact that it is almost impossible to fill the container entirely with the goods under treatment, there being considerable interior clearance, mainly between the top surfaces of the goods and the underside of the cover or lid. Furthermore, such laminated goods before heat treatment are usually in a hard and springy condition, and during the heat treatment process they settle and tend to become bedded into a solid pack, the gas between the component parts of the laminated pack being exuded from the interstices. The effect of this is to leave a substantial volume of atmosphere in the container and to make the ratio of volume of goods to volume of container atmosphere unfavourable. It naturally follows that the greater the volume of atmosphere or unfilled space in the container, in relation to the volume of the goods, the greater will be the dilation of this gas outwards and inwards with heating and cooling respectively, and consequently any effect which such gases may have on the goods is proportionate to the volume of gases so dilated or circulated. A further efiect of the incomplete filling of the container is that the cover or lid, which is necessarily of substantial thickness by reason of its support around the sides, is liable to damage by exposure for considerable periods to excessive temperatures, as the transmission of heat from the lid to the goods is almost entirely by radiation across the gap between the top of the goods and the underside of the lid, and is therefore relatively slow.

My present invention is designed to facilitate and improve the process of heat treatment by limiting or minimizing the unfavourable conditions and results referred to, and with this object in view the invention consists in so constructing. the container as to comprise a base or tray of inverted box formation adapted to support the goods on its raised upper surface, in combination with a lid or cover of inverted box formation adapted to take a floating bearing on the goods thus supported and to be telescopically slidable over and around the base or tray, said base or tray being preferably provided with a series of internal reinforcing ribs.

In order that the invention may be clearly understood and readily carried into practice, reference may be had to the appended explanatory drawing, in which:-

Figure 1 is a sectional elevation of a container constructed in accordance with the invention.

Figure 2 is a similar View of the container in use for the heat treatment of a laminated metal pack- Figure 3 is a plan of the container, in section on a, plane indicated by the line IIIIII in Figure 1.

The tray a which forms the base of the container is provided in the form of an inverted box open at the bottom, and is reinforced by a series of internal ribs b to give supporting strength to the upper surface which supports the goods. The laminated or like goods 0 are placed on the top of the inverted tray a and a cover d is placed over the goods, the underside of this cover (1 resting or bearing on the upper surfaces of the goods 0 as seen in Figure 2.

The cover 01 is also of inverted box formation, its interior dimensions being slightly greater than the exterior dimensions of the supporting tray a, as seen particularly in Figure 3. The side walls of the cover 01 are of a depth approximately equal to the depth of the side walls of the tray a, plus if desired an additional depth slightly less than the minimum thickness of load under treatment, so that at all times the side walls of the cover (1 lap the side walls of the tray a, but never to such an extent as will allow the side walls of the cover :1 to sink to the level of the bottom of the tray a when the container is loaded.

The elfect of this is that the side walls of the tray a, reinforced by the supporting ribs b extending at spaced intervals, always take the full bearing of the load 0, andthat the cover (I is made to float upon and to be supported by the load 0. This floating support of the cover d enhances the efficiency of the process of heat treatment by causing the heat to be transmitted to the goods mainly by conduction through direct contact of the cover with the goods. It also minimizes the liability of damage to the cover by excessive temperatures, as the cover 11 can be made of relatively thin material by reason of the elimination of side supports, and, by reason of its contact with the load, can never assume a temperature materially in excess of that of the load itself.

As the load 0 under treatment becomes soft, and in consequence beds and sinks, so the cover d supported by the load also sinks, and by this means the atmosphere in the container is maintained at minimum volume, and dilation on heating and cooling is correspondingly reduced. As furthermore the goods 0 are elevated considerably above the bearing surface of the tray (1 which rests on the hearth of the furnace, with the lid or cover d bearing on the load, the goods are always maintained in a pocket which is provided at e with a vertical atmospheric seal, thus eliminating during the whole of the heating and cooling cycle any tendency to induce convection currents into and out of the container.

The improved container may be made in circular or rectangular form to suit the class of goods under treatment, and the construction is such as to permit of the container being withdrawn from the furnace at full heat treatment temperature, for discharge by conveyor or otherwise, for instance into cooling chambers or tubes filled with suitable inert gases.

Alternatively the container is adapted for use in association with rotary or annular hearth furnaces fitted with cooling chambers or tubes for receiving the load after discharge.

What I claim as my invention and desire to secure by Letters Patent is:

1. A protective container for metal sheets or like metallic goods during the process of heat treatment, which comprises a base tray of inverted box formation having an upper surface raised on upstanding side walls so as to be adapted to support the goods upon said raised upper surface, in combination with a cover lid of inverted box formation which is vertically and freely slidable over and around said base tray by telescopic and atmospheric sealing engagement between the respective side walls of the cover lid and of the base tray, the sides of said base tray being equal in depth to the sides of said cover lid or of greater depth, whereby said cover lid is adapted to take a continuously floating bearing upon the goods thus supported, irrespective of the depth to which said goods are packed.

2. A protective container for metal sheets or like metallic goods during the process of heat treatment, which comprises in combination a base tray of inverted box formation having an upper surface raised on upstanding side walls so as to be adapted to support the goods upon said raised upper surface, a series of internal reinforcing ribs located Within said base tray in supporting relation to said raised upper surface, and a cover lid of inverted box formation which is vertically and freely slidable over and around said base tray by telescopic and atmospheric sealing engagement between the respective sidewalls of the cover lid and of the base tray, the sides of said base tray being equal in depth to the sides of said cover lid or of greater depth, and said cover lid being adapted to take a continuously floating bearing upon the goods thus supported, irrespective of the depth to which said goods are packed.

JOHN FALLON. 

